For if any man see thee which hast knowledge sit at meat in the idol's temple, shall not the conscience of him which is weak be emboldened to eat those things which are offered to idols; If any man see thee which hast knowledge - Of the true God, and who art reputed for thy skill in Divine things.
Sit at meat in the idol's temple - Is it not strange that any professing the knowledge of the true God should even enter one of those temples? And is it not more surprising that any Christian should be found to feast there? But by all this we may see that the boasted knowledge of the Corinthians had very little depth in things purely spiritual.
There are many curious thin-spun theories in the rabbinical writings concerning entering idol temples, and eating there, and even worshipping there, providing the mind be towards the true God. Dr. Lightfoot produces several quotations to prove this. Perhaps the man of knowledge mentioned by the apostle was one of those who, possessing a convenient conscience, could accommodate himself to all circumstances; be a heathen without and a Christian within, and vice versa, as circumstances might require.
Be emboldened to eat - Οικοδομηθησεται, Be built up - be confirmed and established in that opinion which before he doubtingly held, that on seeing You eat he may be led to think there is no harm in feasting in an idol temple, nor in eating things offered to idols.